Cyclonic vehicular traffic pollution control system

ABSTRACT

A filter may remove PM2.5 and/or other airborne pollutants, which filter has fibers of an average diameter of no more than 500 nm, the fibers of at least 90 wt. % polyacrylonitrile, relative to all fibers in the filter; and a catalyst of at least 90 wt. % TiO2, relative to all catalytic metals in the filter, dispersed onto the fibers. The fibers need not be charged. The TiO2 may be condensed or precipitated onto the fibers out of a liquid containing the TiO2 and the fibers by simple methods. The catalyst may be activated by UV irradiation to decompose particulate matter having an average particle size of 2.5 μm or less, i.e., PM2.5, and/or other airborne pollutants from air. Such filters may be implemented around areas of vehicle traffic, e.g., as elements of traffic lights, and may be used to controllably purify polluted air.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to air purification devices and methods,particularly using TiO₂-coated fibers, which may have nanometer-scaleaverage particulate and/or fiber diameters, and may be particularlyuseful in reducing the amount of airborne particulate matter of averageparticle size up to 2.5 μm (PM_(2.5)) and/or noxious and/or toxicpollutant gases in the air often generated in association with fossilfuel combustion.

Description of the Related Art

The potential health effects of exposure of human populations livingnear major roadways to certain air pollutants and toxins emitted fromboth gasoline and diesel engines are a growing concern. Recenttoxicological and epidemiological studies have identified living nearmajor roadways as a risk factor for respiratory and cardiovascularproblems and other health related issues including asthma, allergicdiseases, reduced lung function, reduced lung growth, low birth weight,pre-term newborns, lung cancer, and premature death. Particulate matterpollution has thus become a serious concern for public health.

Air quality depends on the various gases and particles present in thelocal environment. Both natural phenomena and human activities canaffect the cleanliness of air.

In recent decades, many countries experienced unprecedented industrialgrowth. This industrial growth has improved the quality of life in thesecountries and regions while correspondingly increasing certainenvironmental health risks, particularly airborne pollution.

Recent epidemiological studies have indicated that the exposure to fineparticulate matter, i.e., airborne particulate matter having a particlediameter up to 2.5 μm, or PM_(2.5), is associated with increasedcardiopulmonary morbidity and mortality. Some studies have indicatedthat levels of particulate matter are high in various industrialregions, including metropolitan areas throughout China, the UnitedStates, Europe, and greater India, as well as in Saudi Arabia and otherregions of the Gulf. The airborne particulate issues in the GCC andparticularly Saudi Arabia have mainly been attributed to rapidurbanization, vehicular traffic, industrialization, and an arid climatecharacterized by sand storms.

Airborne particulate matter pollution, left unmanaged, can seriouslydiminish quality of life, and it poses a serious public health threat aswell as influencing visibility, direct and indirect radiative forcing,climate, and ecosystems. Airborne particulate matter is a complexmixture of extremely small particles and liquid droplets. Based on theparticle size, airborne particulate matter is categorized, inter alia,as PM_(2.5) with particle sizes up to 2.5 μm, or PM10, with particlesizes up to 10 μm. PM_(2.5) pollution is particularly harmful since itcan penetrate human bronchi and lungs owing to the small particle size.Long-term exposure to PM_(2.5) increases morbidity and mortality.

Serious airborne particulate matter pollution problems have begun topresent themselves in developing countries with large manufacturingindustries and/or substantial localized fossil fuel combustion, such asSaudi Arabia. Air quality guidelines related to internationalcomparative PM_(2.5) pollution in a number of countries including SaudiArabia are shown in FIG. 1. The complex compositions of airbornePM_(2.5) pollution may include inorganic matter, such as SiO₂, SO₄, NO,and NO₂, and organic matter, such as organic carbon and elementalcarbon, from diverse sources including soil dust, vehicular emission,coal combustion, secondary aerosols, industrial emission, and biomassburning.

PM_(2.5) air pollution has accordingly become a widely studied airpollutant, associated with increased risk of cardiovascular disease,pulmonary disease, kidney disease, and other non-communicable diseases.PM_(2.5) is believed to have contributed to about 4.2 million prematuredeaths in 2015. A growing body of evidence suggests an associationbetween PM_(2.5) pollution and the risk of diabetes. PM_(2.5)concentration was suspected to be responsible for about 432,000premature deaths in Europe in 2016.

Motor-vehicle emissions consist of a complex mixture of particulate andgaseous pollutants, including fine particulate matter, i.e., PM_(2.5),or particles with a diameter no more than 2.5 μm, ultrafine particles,i.e., UFPs, or particles with a diameter no more than 0.1 μm, metals,organic material, black carbon (BC), volatile organic compounds (VOC),nitrogen oxides (NO_(x), mostly NO and NO₂) and carbon monoxide (CO).While PM_(2.5) and NO₂ are currently regulated as critical pollutants,UFPs are not specifically regulated despite having been shown to betoxic and have negative health impacts.

The behavior of PM pollution differs from other pollutants due to theirchemical compositions, morphologies, and mechanical properties. Certainrigid inorganic PM pollutants are mainly captured by interception andimpaction on a filter surface. Some soft PM containing carbon compoundsand/or water, such as those from combustion exhaust, can deform onfilter surfaces and require stronger binding during the process ofattaching to the filter. Studies have focused on the surface propertiesof air filters to enhance PM particle capture. However, in existing airfilter technology, insufficient effort has been invested in studying theproperties of filter materials. There are essentially two types of airfilters in common use. Certain efforts into filter improvements havebeen made in the art that warrant discussion.

CN 104815483 B and CN 204723896 U by Zhang et al. (Zhang) disclose acomposite anti-microbial air filtration material. Zhang's electretfabric layer combines an electrospun fiber membrane layer, chitosan, andnano TiO₂ photocatalyst, and can remove PM_(2.5) while having ananti-microbial, disinfectant, and odor removal function. Zhang'sfiltration material may be used in window curtains and screens,air-conditioners, air purifiers, and masks, to purify indoor air. WhileZhang discloses an electrospun layer optionally made ofpolyacrylonitrile (PAN) among other choices, Zhang requires a chitosanlayer and does not describe a PAN-fiber filter coated with TiO₂ forremoving PM_(2.5) particles from air.

CN 1276224 C by Fu et al. (Fu) discloses an adsorption air purifier withfour parts: a casing, electronic dust collector, photocatalyticdegrading unit, and negative ion generator. Fu's photocatalyticdegrading unit comprises several UV lamps and an active carbonfiber-based photocatalytic TiO₂ material around the lamp tubes. Fu's airpurifier relies on the active carbon fiber, the potential differencebetween the charged pollutant, and the grounded photocatalyst, to absorbairborne pollutant on the surface of the photocatalyst to promote thephotocatalytic process. Fu's device can collect dust andphotocatalytically degrade and ionize pollutants to improve air quality.Fu requires carbon fibers and ionization and does not describe a polymer(e.g., PAN) filter coated with TiO₂, nor does Fu expressly describeremoving PM_(2.5) particles.

CN 105371399 B by Liu et al. (Liu) discloses an air purifying devicewith a ventilating pipeline having an inlet and outlet, a purifyingsystem, and a draft fan. Liu's purifying system has a purifying partarranged in the ventilating pipeline between the inlet and the outlet,the purifying part being manufactured from modified polyacrylonitrilefibers. Liu's device may use a UV lamp and photocatalyst layer such asTiO₂, but Liu's TiO₂ is on a glass fiber coating, not apolyacrylonitrile fiber. Also, Liu's polyacrylonitrile fibers aremodified, Liu does not disclose a cyclone element or specificallyremoving PM_(2.5) particles.

CN 109107395 A by Zhao et al. (Zhao) discloses a gas/air filter, itspreparation, and applications. Zhao's air filter has a nanofibrousmembrane of a high molecular weight polymer (PVB, PAN, PVP, PEO, PMMA,PMA, PA, etc.), made by electrostatic spinning, and a photochemicalcatalyst (TiO₂, ZnO, W₁₈O₄₉, WO₃, etc.) effective to filter outparticulate pollutants such as PM_(2.5) and PM₁₀ in air, applicable toair cleaning facilities such as screen windows, masks, and filterscreens. Zhao's PAN is 150 kDa and Zhao does not particularly describecombining PAN and TiO₂, much less in a device or system comprising acyclone, filter, pump, and UV emitter, nor one located close to vehicletraffic.

CN 109023727 A by Chen et al. (Chen) discloses a nanofiber membranematerial for capturing PM_(2.5) and its preparation, involvingelectrostatic spinning a nano composite fiber filter membrane andcontacting the Chen's filter with particulate matter and PM2.5 in airpolluted by cigarette smoke. Chen describes electrospinning a PAN/TiO₂nano composite fiber filter membrane with to reduce PM_(2.5) pollution,and Chen's fibers are charged.

KR 10-0945311 B1 by Jung (Jung) discloses a complex photocatalyst filterusing visible rays and an air purifying device using the same to removecontaminated materials and bacteria from air. Jung uses a base materialwith a net body and a photocatalytic coating on the surface of the basematerial, suitable to decompose pollutants in the air. Jung'sphotocatalyst composition includes Rh, TiO₂, V₂O₅, WO₃, K₂SIO₃, andPtCl₂. Jung discloses visible light catalysts, and is silent about usingpolyacrylonitrile.

J. Colloid Interf. Sci. 2017, 507, 386-396 by Su et al. (Su-I) disclosesnanoparticle-on-nanofiber composite membranes prepared byelectrospraying TiO₂ suspensions and electrospinning a PAN solutionsimultaneously. Su-I's TiO₂ nanoparticles are dispersed on the surfaceof PAN nanofibers to construct hierarchical nanostructures, providingphotocatalytic activity and filtering capabilities. Su-I's TiO₂ has anaverage particle size of 25 nm and Su-I estimates the amount of TiO₂ inits composite to be 4, 9, 13, and 22 wt. %.

Environ. Sci. Technol. 2013, 47(20), 11562-11568 by Su et al. (Su-II)discloses TiO₂ nanoparticles on electrospun PAN nanofibers via coupledelectrospinning and hydrothermal synthesis. Su-II discloses aphotocatalytic oxidation process for simultaneous desulfurization anddenitrification of flue gas using its TiO₂-PAN photocatalyst. Su-IIdiscloses a titanium loading of 6.78 at. % under UV light was proposed.Su-II does not describe removing PM_(2.5) nanoparticles or a deviceincluding a cyclone, pump, and filter.

Mater. Res. Express 2019, 6(3), 035027 by Xiong et al. (Xiong) disclosesair filters having electrospun nanofiber membranes with small pore sizedistribution for treating airborne particulate matter. Xiong's lowfiltration resistance sandwich structured PAN fibrous filters havecontrolled, accumulated, bimodal sized fibers, i.e., 172±21 nm and772±118 nm. Xiong is silent about using TiO₂ and removing PM_(2.5), CO,and nitrogen oxides.

Aerosol Air Qual. Res. 2017, 17(7), 1909-1916 by Zhang et al. (Zhang)discloses surface charged nanofibers, charged through corona discharge,to filter fine particles. Zhang describes 2.0% TiO₂ polyacrylonitrilefibers with up to 0.97 kV charge. Zhang's fibers are made byelectrospinning and have no more than 2 wt. % TiO₂, and Zhang's filterrelies on electrical charge. Zhang is silent on a cyclone, pump, andfilter in its system.

In light of the above, a need remains for less complicated, yet stilleffective filter materials and methods, particularly for PAN-TiO₂systems, and for simplified methods of making such materials, e.g., bysolution-based coating.

SUMMARY OF THE INVENTION

Aspects of the invention provide methods for removing at least oneairborne contaminant from polluted air. Such methods may comprise:passing polluted air comprising the at least one airborne contaminantthrough a cyclone to remove particles of at least 100 μm, to obtaincycloned air having less of the airborne contaminant than the pollutedair; contacting the cycloned air with an uncharged filter underirradiation by ultraviolet (UV) light, to obtain a filtered air havingless of the airborne contaminant than the cycloned air, wherein thefilter comprises (i) fibers of an average diameter of no more than 500nm, the fibers comprising at least 90 wt. % polyacrylonitrile, relativeto all fibers in the filter, and (ii) a catalyst comprising at least 90wt. % TiO₂, relative to all catalytic metals in the filter, dispersedonto the fibers, and wherein the at least one airborne contaminantcomprises particulate matter having a particle size of 2.5 μm or less,CO, a volatile organic compound, a sulfur oxide, a nitrogen oxide, or acombination of two or more of any of these. Such methods may be modifiedby any feature or combination of features described herein in anypermutation, particularly the following modifications.

The passing and/or the contacting may comprise drawing the polluted airwith a pump. The passing and/or the contacting may be powered byphotovoltaic energy, and the photovoltaic energy may further be storedin one or more batteries configured to the power the passing,contacting, and/or irradiation. Alternatively or additionally, thepassing and/or the contacting may be powered by a municipal electricalpower grid.

The TiO₂ on the fibers may have been precipitated onto the fibers whilein a liquid phase with the fibers.

The irradiation may comprise directing a UV lamp at the filter and/orthe irradiation may comprise sunlight.

Inventive methods may be conducted from a vehicular traffic signal, astreet light, a static traffic sign, a mobile traffic sign, a divider, amobile traffic barrier, a manhole cover, a sewer grating, a trainlevel-crossing, a billboard, a telephone pole, a power pole, or two ormore of any of these. Inventive methods may be conducted in a locationwith no access to municipal electrical power.

Aspects of the invention provide filters, comprising: fibers of anaverage diameter of no more than 500 nm, the fibers comprising at least90 wt. % polyacrylonitrile, relative to all fibers in the filter; and acatalyst comprising at least 90 wt. % TiO₂, relative to all catalyticmetals in the filter, dispersed onto the fibers, wherein the fibers areuncharged, wherein the TiO₂ is condensed onto the fibers out of a liquidcomprising the TiO₂ and the fibers, and wherein the catalyst isactivated by UV irradiation to decompose particulate matter having aparticle size of 2.5 μm or less from air. Such filters may be modifiedby any feature or combination of features described herein in anypermutation.

The TiO₂ may have an average particle diameter of no more than 24 nm,and/or the TiO₂ may be at least 50% anatase.

Inventive filters may be suitable to remove carbon monoxide, a volatileorganic compound, a nitrogen oxide, a sulfur oxide, a further combustionexhaust gas, or a combination of two or more of these, from air.

Inventive filters may be configured to reject particles having adiameter greater than 300 nm.

Aspects of the invention provide air treatment systems, comprising: atleast one inventive filter of any permutation described herein, mountedin a catalytically inactive frame; a cyclone configured to removeairborne particles having an average particle size of 100 μm or more; aUV source; and an electrical power source, wherein the filter ispositioned to receive ultraviolet radiation from the UV source, andwherein the cyclone is operably connected to the filter. Such systemsmay be modified by any feature or combination of features describedherein in any permutation.

Inventive systems may be ones in which the electrical power sourcecomprises a battery and/or a photovoltaic cell.

Inventive systems may further comprise a pump, operably connected to thecyclone and the filter so as to move air through the cyclone and filter.

Aspects of the invention provide methods of synthesizing a particulateair filter material, which methods may comprise: contactingpolyacrylonitrile fibers with an average diameter of no more than 500 nmwith TiO₂ in a liquid; mechanically agitating the liquid comprising thefibers and the TiO₂; and/or removing liquid to provide the particulateair filter material comprising TiO₂ deposited upon the polyacrylonitrilefibers. The mechanically agitating comprises sonicating the liquid. Suchmethods may be modified by any feature or combination of featuresdescribed herein in any permutation.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 shows comparative international PM_(2.5) pollution in a number ofcountries including Saudi Arabia relative to suggested WHO air qualityguidelines;

FIG. 2 shows an exemplary percent composition of polluted air byharmfulness to the general population;

FIG. 3 shows an exemplary representation of elements of animplementation of the inventive filter system in a traffic signalsetting;

FIG. 4 shows a schematic flowchart of a preparation of exemplary filterfibers prepared with solutions of 5 mg/mL, 10 mg/mL and 15 mg/mL TiO₂versus a control (no TiO₂);

FIG. 5 shows a comparative chart of PM_(2.5) removal by a control filterand exemplary filters having polyacrylonitrile fibers coated withdifferent TiO₂ nanoparticle concentrations;

FIG. 6 shows a comparative plot of toxic gaseous air pollutants removalby a control filter and exemplary filters having polyacrylonitrilefibers coated with different TiO₂ nanoparticle concentrations;

FIG. 7A shows a scanning electron microscope (SEM) image of a controlfilter having polyacrylonitrile (PAN) fibers and no TiO₂ on a 5 μmscale;

FIG. 7B shows an SEM image of an exemplary inventive filter having PANfibers coated with 5 mg/mL TiO₂ on a 5 μm scale;

FIG. 7C shows an SEM image of an exemplary inventive filter having PANfibers coated with 10 mg/mL TiO₂ on a 5 μm scale;

FIG. 7D shows an SEM image of an exemplary inventive filter having PANfibers coated with 15 mg/mL TiO₂ on a 5 μm scale; and

FIG. 8 shows PM_(2.5) removal efficiency for different TiO₂ nanoparticleconcentrations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Aspects of the invention provide methods for removing at least oneairborne contaminant from polluted air. Such methods may comprise:passing polluted air comprising the at least one airborne contaminantthrough a cyclone to remove particles of, e.g., at least 100, 90, 80,75, 67, 60, 50, 40, 35, 30, 25, 20, 17.5, 15, 12.5, or 10 μm, to obtaincycloned air having less of the airborne contaminant than the pollutedair; contacting the cycloned air with an uncharged filter underirradiation by ultraviolet (UV) light, to obtain a filtered air havingless of the airborne contaminant than the cycloned air, wherein thefilter comprises (i) fibers of an average diameter of no more than 500nm, e.g., no more than 500, 475, 450, 425, 400, 375, 350, 333, 325, 315,300, 285, 275, 267, 250, 233, 225, 215, 210, 205, or 200 nm, the fiberscomprising at least 90 wt. % polyacrylonitrile, e.g., 90, 91, 92, 92.5,93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % PAN (or evenconsisting essentially of—i.e., not having more than 5, 4, 3, 2.5, 2, 1,0.5, 0.1, 0.01, 0.001, 0.0001, or 0.00001% monomers other thanacrylonitrile), relative to all fibers in the filter, and (ii) acatalyst comprising at least 90 wt. % TiO₂, e.g., 90, 91, 92, 92.5, 93,94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % TiO₂, relativeto all catalytic metals in the filter, dispersed onto the fibers, andwherein the at least one airborne contaminant comprises particulatematter having a particle size of 2.5 μm or less, e.g., no more than 2.5,2.45, 2.4, 2.35, 2.33, 2.3, 2.25, 2.2, 2.15, 2.1, 2.05, or 2.0 μm and/orat least 0.1, 0.25, 0.5, 0.6, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1 μm,CO (carbon monoxide), a volatile organic compound as described below, asulfur oxide as described below, a nitrogen oxide as described below, ora combination of two or more of any of these. The passing and/or thecontacting may comprise drawing the polluted air with a pump asdescribed below. Generally, the pump may be arranged downstream of thefilter in a system that is substantially or completely closed betweenthe filter (housing) and the cyclone (housing), so as to urge gaseousfluid through the filtration system and expel purified gas (air) beyondthe pump downstream of the filter.

The TiO₂ on the fibers may have been precipitated onto the fibers whilein a liquid phase with the fibers. Rather than electrospraying the TiO₂,and/or affixing it to the PAN in any other way, the TiO₂ is preferablyadsorbed to the surface of the PAN fibers from a liquid, e.g.,suspension, colloid, or solution, of TiO₂ in a solvent (or liquid inwhich the TiO₂ is only partially soluble or insoluble).

Relevant solvents may include pyridine, N,N-dimethylformamide (DMF),N,N-dimethylacetamide, N-methyl pyrrolidone (NMP),hexamethylphosphoramide (HMPA), dimethyl sulfoxide (DMSO), acetonitrile,tetrahydrofuran (THF), 1,4-dioxane, dichloromethane, chloroform, carbontetrachloride, dichloroethane, acetone, ethyl acetate, pet ether,pentane, hexane(s), cyclohexane, decane(s), decalin, THF, dioxane,benzene, toluene, xylene(s), o-dichlorobenzene, diethyl ether, methylt-butyl ether, diisopropyl ether, ethylene glycol, methanol, ethanol,isopropanol, propanol, n-butanol, isobutanol, amyl alcohol, isoamylalcohol, cyclopentanol, hexan-1-ol, hexan-2-ol, hexan-3-ol,2-methylpentan-1-ol, 3-methylpentan-1-ol, 4-methylpentan-1-ol,2-methylpentan-2-ol, 3-methylpentan-2-ol, 4-methylpentan-2-ol,2-methylpentan-3-ol, 3-methylpentan-3-ol, 2,2-dimethylbutan-1-ol,2,3-dimethylbutan-1-ol, 3,3-dimethylbutan-1-ol, 2,3-dimethylbutan-2-ol,3,3-dimethylbutan-2-ol, 2-ethylbutan-1-ol, cyclohexanol, and/or water.

The irradiation may comprise directing a UV lamp at the filter and/orthe irradiation may comprise sunlight, e.g., the filter may be exposedto direct sunlight (for example, with a glass, PC, or material otherwisetransparent to UV) and/or indirect sunlight (for example, with a mirrorsystem). Useful UV lamps may include a UV curing lamp, UV mediumpressure lamp, UV low pressure lamp, UV amalgam lamp, filtered UV lamp,high intensity UV lamp, black-light UV lamps, UV germicidal lamp, UV-LEDlamp, or a combination of 2, 3, 4, 5, 6, 7, . . . 10 or more of these.Relevant UV lamps may have a spectral output of 254 nm and beozone-free, and/or may include standard low-pressure mercury lamps(ozone-generating) made of synthetic or natural quartz glass havingspectral output at 365, 254, and/or 185 nm. Relevant UV lamps may haveUV output that drops to 50% after 8,000 hours of operation, or provideup to 90% of the UVC output even after 16,000 hours of operation. UVlamps may have a UV efficiency of at least 25, 27.5, 30, 32.5 35, 37.5,40, 42.5, 45% or more. Relevant UV lamps may have emission wavelengthsas described below (e.g., a range of 100, 125, 150, 175, or 200 nm to400, 425, 450, 475, 500, 525, 550, 575, 600, 650, 700, 750, or 800 nm)and/or a power density of, e.g., at least 25, 50, 75, 80, 85, 90, 95,100, 110, 117.5, 125, 133, 140, 150, 165, 175, 200, 250, 500, or 1000W/cm²

The passing and/or the contacting may be powered by photovoltaic energy,and the photovoltaic energy may further be stored in one or morebatteries (1, 2, 3, 4, 5, 6, 7 . . . 10, etc.) configured to the powerthe passing, contacting, and/or irradiation. Alternatively oradditionally, the passing and/or the contacting may be powered by amunicipal electrical power grid. Batteries relevant for inventivesystems and/or methods are generally rechargeable, and may include analuminum-ion, carbon (single carbon or dual carbon), flow, vanadiumredox, zinc-bromine, zinc-cerium, lead-acid (e.g., deep cycle, VRLA,AGM, gel, etc.), glass battery, lithium-ion (lithium ion lithium cobaltoxide (ICR), lithium ion manganese oxide (IMR), lithium ion polymer,lithium iron phosphate, lithium-sulfur, lithium-titanate, thin filmlithium-ion, lithium ceramic), magnesium-ion, metal-air electrochemicalcell (e.g., lithium air, aluminum-air, germanium air, calcium air, ironair, potassium-ion, silicon-air, zinc-air, tin air, sodium-air,beryllium air, etc.), molten salt, nickel-cadmium (e.g., nickel-cadmiumbattery vented cell type), nickel hydrogen, nickel-iron, nickel metalhydride (e.g., low self-discharge NiMH), nickel-zinc, organic radical,polymer-based, polysulfide bromide, potassium-ion, rechargeablealkaline, rechargeable fuel, sand, silicon air, silver-zinc, silvercalcium, silver-cadmium, sodium-ion, sodium-sulfur, solid-state, superiron, UltraBattery®, and/or zinc ion batteries, or combinations of twoor more of any of these.

Inventive methods may be conducted from a vehicular traffic signal, astreet light, a static traffic sign, a mobile traffic sign, a divider, amobile traffic barrier, a manhole cover, a sewer grating, a trainlevel-crossing, a billboard, a telephone pole, a power pole, or two ormore of any of these. Inventive filters, devices containing the filters,and/or systems containing these may be incorporated into a vehiculartraffic signal, a street light, a static traffic sign, a mobile trafficsign, a divider, a mobile traffic barrier, a manhole cover, a sewergrating, a train level-crossing, a billboard, a telephone pole, a powerpole, or two or more of any of these. That is, inventive systems, may beentirely or partially integrally installed into any of thesetraffic/transportation fixtures (including those described below),and/or at least partially included, at least partially, in a separatehousing on or within 1000, 750, 500, 250, 150, 100, 75, 50, 45, 40, 35,30, 25, 20, 15, 10, or 5 cm of such fixtures. Inventive methods may beconducted in a location with no access to municipal electrical power,i.e., in an isolated and/or remote location, e.g., distant from cities,off the grid, at high altitude, or otherwise inaccessible or relativelyunapproachable. It may also be relevant to practice inventive methodsand/or implement inventive systems in populated or otherwise non-remoteareas at which cabling are undesirable.

Aspects of the invention provide filters, comprising: fibers of anaverage diameter of no more than 500 nm (e.g., any diameter describedabove or below), the fibers comprising at least 90 wt. %polyacrylonitrile (e.g., any weight percent described above or below),relative to all fibers in the filter; and a catalyst comprising at least90 wt. % TiO₂ (e.g., any weight percent described above or below),relative to all catalytic metals in the filter, dispersed onto thefibers, wherein the fibers are uncharged, wherein the TiO₂ is condensedonto the fibers out of a liquid comprising the TiO₂ and the fibers, andwherein the catalyst is activated by UV irradiation to decomposeparticulate matter having a particle size of 2.5 μm or less (e.g., anydiameter described above or below) from air.

The TiO₂ may have an average particle diameter of less than 25 nm or nomore than 24, 23, 22, 21, 20, 19, 18, 17.5, 17, 16, or 15 nm. The TiO₂may be at least 50, 60, 70, 75, 80, 85, 90, 91, 92, 92.5, 93, 94, 95,96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9% anatase and/or no more than50, 33, 25, 20, 15, 10, 7.5, 5, 2.5, 2, 1, or 0.1% rutile.

Inventive filters may be suitable to remove UFPM, PM_(2.5), PM₅,PM_(7.5), PM₁₀, carbon monoxide, a volatile organic compound (asdescribed below), a nitrogen oxide (as described below), a sulfur oxide(as described below), a further combustion exhaust gas (as describedbelow), or a combination of two or more of these, from air. Inventivefilters may be configured to reject particles having a diameter greaterthan 300, 285, 275, 265, 250, 240, 233, 225, 220, 210, 200, 190, 180,175, 170, 160, 150, 140, 130, 120, 110, or 100 nm.

Aspects of the invention provide air treatment systems, comprising: atleast one inventive filter of any permutation described herein, mountedin a catalytically inactive frame; a cyclone configured to removeairborne particles having an average particle size of 100 μm or more; aUV source; and an electrical power source, wherein the filter ispositioned to receive ultraviolet radiation from the UV source, andwherein the cyclone is operably connected to the filter.

Inventive systems may be ones in which the electrical power sourcecomprises a battery (one or more as described above) and/or aphotovoltaic (solar) cell. Relevant photovoltaic cells may includecrystalline silicon, polysilicon, thin film solar cells, amorphoussilicon, Cd—Te, CIGS (Cu—In—Ge—Se), mono-like-multi silicon (MLM),gallium arsenide (GaAs), etc., as well as multiple junction cells, suchas GaInP/Si dual junction solar cells. If photovoltaic units areimplemented in inventive methods and systems, the photovoltaic units(and/or the batteries) do not need to be located directly together withthe filter(s), optional UV lamp(s), and/or cyclone(s), or even the pump.Photovoltaic and/or battery power sources may be fed by cables/linesdistanced from the filter, etc., e.g., 10, 7500, 5000, 2500, 1000, 750,500, 250, 100, 75, 50, 25, 15, 10, or 5 m away. Theoretically, the pumpand/or the cyclone may be spaced from the filter by extended distances,e.g., independently 50, 40, 30, 25, 20, 25, 10, 9, 8, 7, 6, 5, 4, 3, 2,1 m, though for practical reasons preferably not as far as power cables(e.g., due to increased potential for leaks in the lines).

Inventive systems may further comprise 1, 2, 3, 4, 5, etc. pump(s) asdescribed herein, operably connected to the cyclone and the filter so asto move air through the cyclone and filter.

Aspects of the invention provide methods of synthesizing a particulateair filter material, which methods may comprise: contactingpolyacrylonitrile fibers with an average diameter of no more than 500 nmwith TiO₂ in a liquid; mechanically agitating the liquid comprising thefibers and the TiO₂; and/or removing liquid to provide the particulateair filter material comprising TiO₂ deposited upon the polyacrylonitrilefibers. The mechanically agitating comprises sonicating the liquid,e.g., for at least 10, 15, 20, 25, 30, 35, 45, 60, 120, or 150 minutesand/or no more than 300, 240, 180, 120, or 60 minutes. The sonicationmay be at 40±1, 2, 2.5, 3, 4, 5, 10, 15, 20, 25, or 30 KHz.

Inventive methods of making the filter material can avoidelectrospinning and electrospraying completely, and inventivefibers/filters are configured to operate without a charge (uncharged orneutral). Inventive filters may include single layers of a singleconcentration, multiple layers of a single concentration, or multiplelayers of varying concentrations. The concentration of TiO₂ on the PANfibers may be, for example, at least 0.5, 1, 2.5, 3, 4, 5, 6, 7.5, 10,12.5, 15, 17.5, 20, 22.5, 25, 30, or 33 wt. % and/or up to 50, 45, 40,35, 33, 30, 27.5, 25, 22.5, 20, 17.5, 15, 14, 13, 12, 11, 10, 9, 8, 7,6, or 5 wt. %. Inventive fibers and/or filters need not comprisechitosan (e.g., carboxylated chitosan-carboxymethyl chitosan, chitosanoligosaccharide, hyaluronic acid-like chitosan, chitosan salt—chitosansulfate, chitosan hydrochloride, chitosan quaternary ammonium salt,chitosan lactate, chitosan glutamate, etc.) and/or polymers with amineside groups, or may comprise no more than 5, 4, 3, 2.5, 2, 1, 0.5, 0.1,0.01, 0.001, 0.0001, or 0.00001 wt. %, relative to total fiber and/orfilter weight, of such amine-containing polymers.

Inventive fibers and/or filters need not comprise polyethylene,polypropylene, modified polyacrylonitrile, polytetrafluoroethylene,hexafluoroethylene, polytrifluoroethylene, polyester, polyethersulfone,polysulfone, polyvinyl alcohol, polyethylene oxide, polylactic acid,polyacrylate, polymethacrylate, poly methyl methacrylate, polyurethane,polyvinylidene fluoride, polyamide, and/or polystyrene, or may compriseno more than 5, 4, 3, 2.5, 2, 1, 0.5, 0.1, 0.01, 0.001, 0.0001, or0.00001 wt. %, relative to total fiber and/or filter weight, of suchamine-containing polymers, either individually or cumulatively.

Inventive filters generally do not contain activate carbon, graphite,graphene, (active) carbon fibers and/or fullerenes, or may comprise nomore than 5, 4, 3, 2.5, 2, 1, 0.5, 0.1, 0.01, 0.001, 0.0001, or 0.00001wt. %, relative to total filter material weight, of such carbonmaterials, either individually or cumulatively.

Inventive devices do not require ion generators, and inventive filtermaterials are generally uncharged, e.g., have no or no more than one (1)charge per 100, 250, 500, 750, 1000, 2500, 5000, 10000, 25000 g/mol, ormore of molecule/polymer. Inventive fibers generally do not includesteel mesh, aluminum mesh, copper mesh, and/or glass fibers, or maycomprise no more than 5, 4, 3, 2.5, 2, 1, 0.5, 0.1, 0.01, 0.001, 0.0001,or 0.00001 wt. %, relative to total fiber weight, of such inorganicmeshes, either individually or cumulatively.

Aspects of the invention provide filters chemically treated with TiO₂which can tolerate and/or remove, e.g., traffic exhaust smoke which maycontain a variety of pollutant gases, including CO, CO₂, NO₂, NH₃, SO₂,NO, N₂O, N₄O, N₂O₃, N₂O₄, N₂O₅, N(NO₂)₃, N₄O₆, O₃, soot, partiallycombusted hydrocarbons, C, monoterpenes, SO, SO₂, SO₃, S₇O₂, S₆O₂, S₂O₂,peroxyacetyl nitrate (C₂H₃NO₅), ionic gases, such as dinitramide(N(NO₂)₃ ⁻), nitrite (NO₂ ⁻), nitrate (NO₃ ⁻), trioxodinitrate (N₂O₃²⁻), peroxonitrite (ONO₂ ⁻), hyponitrite (N₂O₂ ²⁻), nitroxylate (NO⁻),nitronium (NO₂ ⁺), nitrosonium (NO⁺), and volatile organic compounds,such as benzene, toluene, xylenes, acrolein, aldehydes (e.g.,formaldehyde, acetaldehyde, etc.), and polycyclic aromatic hydrocarbons,and convert them into CO₂ and water. Aspects of the invention includeairborne PM_(2.5) removal devices that may be less expensive and/orrequiring less energy than those presently available. Aspects of theinvention include airborne PM_(2.5) removal devices that can be operatedwith solar energy, optionally further with storage batteries attached tosuch devices.

In inventive devices and/or methods, contaminated air may be drawnautomatically through a filter and/or host space for catalyst,optionally using battery operated suction pump. Contaminated air maypass through the cyclone, i.e., dust sizing, which may be configured fordust of average particle diameter of 100 μm or more, and separation,and/or may allow for the passage of respirable dust, e.g., dust ofaverage particle diameters ranging from 1 to 10 μm.

Fine and ultra-fine dust, including PM_(2.5), may be passed to TiO₂chemically treated polyacrylonitrile filter, or comparable material. Thecontact with TiO₂ may occur under UV-exposure, e.g., using one or moreUV-lamps with specific power and/or wavelength(s), and/or from the sun.The irradiation of active TiO₂ photocatalysts may begin with aninteraction of TiO₂ with PM_(2.5) and/or other pollutants, e.g., toxicgases, in the presence of UV light, for example, from one or moreirradiating UV light sources, whereby PM_(2.5) and/or ultra-fine dustcan be captured and adsorbed along the surface area of the TiO₂ filter,and substantially all (e.g., at least 75, 80, 85, 90, 91, 92, 92.5, 93,94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % of a totalweight of such compounds in the inlet gas) toxic gases/pollutants can bebroken down to non-toxic products, such as CO₂, water, and the like.Such a process can provide clean or at least cleaner air asexhaust/output out of the TiO₂ filter, e.g., by reducing the amount ofone or more relevant pollutants to no more than 40, 33, 25, 20, 15, 10,7.5, 5, 4, 3, 2, 1, or 0.5 wt. %, of their original amount(s), upon onecycle.

Inventive methods and devices may be operated at traffic signals, e.g.,when the signal is red and automatically stopped when the traffic signaltransformed to green alternatively, for example, at trafficintersections. The methods and/or devices may continuously operate,and/or be set to operate on particular schedules, such as peak traffictimes. The system may use a municipal energy grid, and/or stored batteryenergy, which may be operated with a photovoltaic (solar) energy panel,e.g., located above the traffic signal. Inventive devices and methodsmay run without a battery on only solar energy during sunlit hours. Thedevice may be installed in traffic signals at traffic intersections soas to operate (e.g., and stop) changeably with the ON and OFF thetraffic signals.

TiO₂ has surprisingly exhibited efficient and effective results inreducing the concentration of PM_(2.5) and toxic gases, substantially(independently, e.g., at least 75, 80, 85, 90, 92.5, 95, 97.5, 98, 99,99.1, 99.5, or 99.9 mol. %) potentially completely reacting these withTiO₂-treated filters and substantially to completely (independently,e.g., at least 50, 60, 70, 75, 80, 85, 90, of 95, 96, 97, 98, 99, 99.5,or 99.9 mol. %) adsorb onto the nanoscale, large surface areaTiO₂-containing filter, e.g., exploiting the photocatalytic power ofTiO₂, preferably in presence of a source of UV light, such as sunlightand/or a UV lamp. Relevant UV light wavelengths may be, for example, atleast 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, or 300 nmand/or up to 1000, 900, 800, 750, 700, 650, 600, 550, 500, 450, 400,350, or 300 nm. The irradiation may use sunlight or an artificial light(e.g., from a lamp), including broad wavelength UV and/or visible light,e.g., from 10 to 1000 nm, or fractions thereof, such as ranges includingendpoints selected from 100±5, 10, 20, 25, 30, 40, or 50, 200±5, 10, 20,25, 30, 40, or 50, 300±5, 10, 20, 25, 30, 40, or 50, 400±5, 10, 20, 25,30, 40, or 50, 500±5, 10, 20, 25, 30, 40, or 50, 600±5, 10, 20, 25, 30,40, or 50, 700±5, 10, 20, 25, 30, 40, or 50, 800±5, 10, 20, 25, 30, 40,or 50, or 900±5, 10, 20, 25, 30, 40, or 50 nm.

By controlling the surface chemistry of the filters, the adhesion ofand/or affinity to airborne particulate matter, e.g., by chemical class,size, polarity, electronegativity, neutrality, etc., can be tailored. Inaddition or separately, the nanostructure of the air filters can beconfigured to promote strong(er) surface adhesion, to increase thecapture possibilities and/or modalities, to modify the air flux, and/orto render more effective the TiO₂ nano-particle chemically treated fiber(e.g., polyacrylonitrile) filters. Removal efficiencies of 90, 91, 92,92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9%, calculatedby comparing the number concentration before and after filtration) forPM_(2.5) can be achieved, even under extreme hazardous air-qualityconditions (e.g., 1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.5, 4, 5,7.5, or 10-times the WHO guideline) in highly polluted traffic areas,particularly when the fiber diameter is decreased to the nanometerscale, under the same packing density. The particle-capture capabilityof inventive devices may be increased by increasing the surface area,i.e., by reducing fiber diameter while maintaining bulk density, whichmay ensure effective particulate matter, e.g., UFPM, PM 2.5, and/orPM₁₀, capture with thinner filters than conventional materials.

Aspects of the invention use filters chemically treated with TiO₂ forremoving the PM_(2.5) and/or other toxic gases/pollutants fromcontaminated air emission, for example, at traffic signals,intersections, along road fencing, at street lights, on telephone poles,in tunnel walls, along overpasses, along underpasses, on electrical(and/or other utility) boxes, on billboards, on facades adjacent tothoroughfares, on cell phone towers, at emergency telephone boxes, etc.,or combinations of these.

Inventive filters may be subjected to chemical treatment and coating ofdifferent concentrations of TiO₂ on the filter to achieve desirednanoscale surface area coverage on the filter, so as to enable them toact as removers for, e.g., UFPM, PM_(2.5), PM₁₀, soot, partiallycombusted hydrocarbons, nitrogen oxides, sulfur oxides, VOCs, and/orother toxic gases, from contaminated air as shown in the an exemplarydesign in FIG. 3.

Inventive devices, configured to remove, e.g., PM_(2.5) and/or othertoxic/pollutant gases, may be less expensive, may use less energy, maybe operated with storage batteries, may be operated from solar energy,e.g., photovoltaic panel(s), and/or the TiO₂-treated filter may bemanufacturing locally by a straightforward process. Inventive devicesmay be highly efficient for PM_(2.5) and/or for all toxic gasesexhausted from traffic and motor vehicle combustion. Such devices may beconfigured to be selective, e.g., for PM_(2.5) relative to PM₁₀,PM_(2.5) relative to UFPM, PM_(2.5) relative to polar pollutants, and/orPM_(2.5) relative to charged and/or uncharged pollutants. Inventivedevices can be used indoor and/or outdoor, e.g., for air purification,to reduce health risks from PM_(2.5) and/or other toxic gas exposures.Inventive devices may be used as separate air cleaning units, e.g., toremove vehicle emissions from the vehicle exhaust prior to emission intothe environment.

Potential applications for inventive devices and methods includeindustrial environments, such as coal-fired, gas, and/or oil-fired powerplants, waste combustion plants, incinerators, cement plants, asphaltplants, refineries, MTO facilities, MTG facilities, crackers,Fischer-Tropsch reactors, etc., in traffic emissions control, such assignage, street lights, traffic signals, billboards, window frames,utility modules, sewer systems (manholes, etc.), crossing signals,speaker systems (e.g., at crossings), facades, tree-mounted fixtures,dividers, walls, overpasses, underpasses, sensors, speed detectors,etc., indoor environments, such as in ventilators, cooling ducts,heating ducts, doors, window sills, etc.

Forms of TiO₂ useful in inventive materials may have an average particlediameter of at least 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 7.5,8, 9, 10, 12.5, or 15 nm and/or up to 50, 45, 40, 35, 30, 25, 24, 23,22.5, 22, 21, 20, 19, 18, 17.5, 17, 16, 15.5, or 15 nm.

Useful TiO₂ may have a BET surface area of, e.g., at least 10, 15, 20,25, 30, 35, 40, 45, 50 m²/g and/or up to 150, 140, 133, 125, 120, 115,110, 105, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, or 50 m²/g. The TiO₂may have a density of, e.g., at least 3, 3.25, 3.5, 3.75, 3.775, 3.8,3.825, 3.85, 3.875, 3.9, 3.925, or 3.95 g/cm³ and/or up to 4.5, 4.4,4.33, 4.25, 4.2, 4.15, 4.1, 4.05, 4.0.25, 4, 3.975, 3.95, 3.925, 3.9,3.875, 3.85, 3.825, 3.8, or 3.75 g/cm³.

Useful TiO₂ materials may have a bulk density of, e.g., at least 0.025,0.0275, 0.03, 0.0325, 0.0333, 0.034, 0.035, 0.036, 0.037, 0.038, 0.039,0.0395, 0.04, 0.0405, 0.041, 0.042, 0.043, 0.044, 0.045, 0.046, 0.047,0.0475, 0.048, 0.049, or 0.05 g/cm³ and/or up to 0.07, 0.069, 0.068,0.067, 0.066, 0.065, 0.064, 0.0633, 0.0625, 0.062, 0.061, 0.06, 0.059,0.058, 0.057, 0.056, 0.055, 0.054, 0.053, 0.052, 0.051, or 0.05 g/cm³.

Useful TiO₂ may be at least 50, 60, 70, 75, 80, 85, 90, 92.5, 95, 97.5,99, or 99.5 wt. % in anatase form.

Useful TiO₂ may be no more than 40, 33, 25, 20, 15, 10, 7.5, 5, 4, 3, 2,1, or 0.5 wt. % in rutile form.

Useful polyacrylonitrile materials may include those having an averagediameter of, e.g., at least 25, 50, 75, 100, 125, 150, 175, 185, 190,195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, or 250 nm and/orup to 1000, 750, 600, 500, 450, 400, 375, 350, 325, 300, 275, 250, 225,220, 215, 210, 205, 200, 195, 190, 185, 180, or 175 nm, and the fibernetwork may be suitable to filter out particles above 250, 240, 230,225, 220, 215, 210, 205, 200, 195, 190, 185, 180, 175, 165, 150, 125,100, or 75 nm.

Useful PAN materials may have a Mn of, e.g., at least 25, 50, 60, 70,75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 133, 140, 150, 175, or200 kDa and/or up to 800, 700, 600, 500, 450, 400, 350, 300, 250, 200,175, 150, 145, 140, 135, 130, 125, 115, or 100 kDa. Useful PANpowders/materials may have a polydispersity index (PDI) of, e.g., atleast 1.01, 1.025, 1.05, 1.1, 1.15, 1.2, 1.25, 1.33, 1.4, 1.45, 1.5,1.6, 1.75, 1.85, 2, 2.25, 2.5, or 3 and/or up to 10, 7.5, 6.5, 5.5, 5,4.5, 4, 3.75, 3.5, 3.25, 3, 2.75, 2.5, 2.25, 2, 1.9, 1.85, 1.8, 1.75,1.7, 1.65, 1.6, 1.55, 1.5, 1.45, 1.4, 1.35, or 1.3. The polymer'smolecular weight distribution may be monomodal, bimodal, trimodal,tetramodal, etc.

Useful PAN materials are generally not modified, e.g., carboxylated,aminated, partially reduced, or the like.

EXAMPLES

Inventive filter materials may be prepared by a method as follows. 2.8gm of Polyacrylonitrile (PAN) fibers (CAS No. 25014-41-10) obtained fromSigma Aldrich, 181315, average Mw: 150,000 g/mol, density 1.184 g/mL at25° C. (lit.) and with a polydispersity index (PDI Mw/Mn): 1.07, withlow Melt flow index (MFI) are contacted with a solvent, such asisopropyl alcohol (Fisher Scientific, USA), in a solution comprisingTiO₂ nanoparticles (nano powder of titanium dioxide—titanium(IV) oxideanatase nano powder, 99.7% purity, lot #13177E0801, UFC Biotechnology,USA). The TiO₂ used had an average particle size less than 21 nm. Theexemplary nano TiO₂ solutions had concentrations of 5 mg/mL, 10 mg/mL,and 15 mg/mL.

The coated fibers were then irradiated with UV light 365 nm to coat thenanoscale TiO₂ onto the nanoscale polyacrylonitrile (PAN) fibers, asdepicted in FIG. 4.

Then all solutions/suspensions were sonicated at 40 KHz for 30 minutesand left to dry at 55° C. for 1 hour.

Nano-filters were installed onto the sampling filter area andsubsequently irradiated with UV light prior to use. The nano-filterswere continuously irradiated with UV light during the sampling time.

The nano-filter fibers may be coated with TiO₂ such that (on themacroscopic surface area of the fibers) at least 40, 50, 65, 75, 80, 85,90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9%of the filter surface area is covered with TiO₂, as is shown in thescanning electron microscope (SEM) image on the right of FIG. 4.

Tests were conducted, sampling air emissions at traffic intersectionsduring red lights at sampling flow rate of 10 L/minute and theconcentration levels of pollutants in inlet air and outlet air, i.e.,after contact with an inventive nanofibrous polyacrylonitrile filterunder UV irradiation, and PM_(2.5) and toxic gases in the air sampleswere analyzed.

Data obtained from the and SEM images of untreated and treated nanofiberpolyacrylonitrile (PAN) filters are disclosed in FIGS. 5 to 7D, as wellas in Tables 1 and 2 below.

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views.

FIG. 1 shows an international comparison of certain locations ornational averages for air pollution relative to the World HealthOrganization (WHO) guideline for airborne pollution concentrationlimits, i.e., 20 μg/m³.

FIG. 2 shows a percentage breakdown of the composition of typicalpollutants in the air and their effect on the human population byseverity.

FIG. 3 shows an exemplary implementation of inventive filter materials,depicting an exemplary photovoltaic cell/collector (1) atop a trafficsignal (2), a battery (4) that may be placed within the pole (3) hostingthe traffic signal (2). An exemplary pump arrangement is driven by thebattery (4), whereby the pump (5) is electrically connected to thebattery (4), and the pump (5) draws polluted air (9) from right to leftthrough a cyclone particle separator (8), then the filter (6), and outthrough the exhaust (10) of the pump (5) back into the environment.

In the arrangement depicted in FIG. 3, the electrical power (4) isprovided by a battery (4) attached to the photovoltaic cells (1), thoughthe air draw may be powered by the photovoltaic cells (1), the municipaland/or local power grid (not numbered), any kind of battery system(e.g., 5), or a combination of these.

In the arrangement depicted in FIG. 3, the filter material (6) is hostedwithin a frame or cartridge upon which UV lamps (5) are mounted. The UVsource may, however, be sunlight and/or some artificial source of UV.Relevant pumps (5) useful in arrangements according to the invention maybe oil pumps, piezoelectrically driven pumps, rotary lobe pumps,progressing cavity pumps, rotary gear pumps, piston pumps, diaphragm(membrane) pumps, screw pumps, gear pumps, vane pumps, peristaltic hose,(vertical and/or horizontal) centrifugal pumps, etc., or combinations ofthese. The pump may be directly powered by a solar cell, by a battery,and/or off the municipal grid.

FIG. 4 shows a schematic representation of a manner of synthesizinginventive TiO₂-containing filter materials, illustrating a control(above) being placed in a solvent and exemplary filter fibers beingplaced in solvent containing selected amounts of TiO₂. The fiber-TiO₂suspensions are then sonicated for a period of time to ensuremixing/dispersion, e.g., at least 5, 10, 15, 20, 25, 30, 40, 45, 60, or90 minutes and/or up to 120, 105, 90, 75, 60, 45, or 30 minutes. Afterdrying, a TiO₂-coated polymer (e.g., PAN) fiber filter material isobtained.

FIG. 5 shows experimental results with the exemplary TiO₂-coated polymer(e.g., PAN) fiber filters on polluted air containing PM_(2.5). Thenumerical data behind FIG. 5 is also presented below in Table 1.

TABLE 1 PM_(2.5) removal by PAN filter coated with different TiO₂concentrations. inlet PM_(2.5) outlet PM_(2.5) Removal Filter Coating(μg/m³) (μg/m³) Efficiency % no TiO₂ 71 41 17.3  5 mg/mL TiO₂ 78 16 48.710 mg/mL TiO₂ 76 9 84.4 15 mg/mL TiO₂ 78 0.5 156

FIG. 6 shows experimental results with the exemplary TiO₂-coated polymer(e.g., PAN) fiber filters on polluted air containing carbon monoxide(CO), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), volatile organiccompounds (VOCs), and ozone (O₃). The numerical data behind FIG. 6 isalso presented below in Table 2.

TABLE 2 Toxic gaseous air pollutant removal by exemplary TiO₂-coated PANfilters. CO CO NO₂ NO₂ SO₂ SO₂ VOCs VOCs O₃ O₃ ppm ppm ppm ppm ppm ppmppm ppm ppm ppm Filter Coating (inlet) (outlet) (inlet) (outlet) (inlet)(outlet) (inlet) (outlet) (inlet) (outlet) no TiO₂ 2.3 1.9 0.46 0.45 0.40.39 0.6 0.45 0.09 0.091 5 mg/mL TiO₂ 2.4 1.5 0.48 0.29 0.45 0.28 0.450.21 0.081 0.04 10 mg/mL TiO₂ 3.1 0.9 0.52 0.18 0.5 0.14 0.4 0.12 0.0910.02 15 mg/mL TiO₂ 2.9 0.3 0.54 0.03 0.52 0.08 0.4 0.05 0.09 0.009

FIG. 7A to 7D show scanning electron microscope (SEM) images of acontrol PAN-fiber filter material (FIG. 7A) and an exemplary inventivePAN-fiber filter material treated with 0.5 mg/mL TiO₂ in isoamyl alcohol(FIG. 7B), an exemplary inventive PAN-fiber filter material treated with10 mg/mL TiO₂ in isoamyl alcohol (FIG. 7C), and an exemplary inventivePAN-fiber filter material treated with 15 mg/mL TiO₂ in isoamyl alcohol(FIG. 7D) on 5 μm scale.

The SEM images disclose increasingly more densely coated nanofibershaving TiO₂ deposits on their surfaces.

Useful fibers may have average diameters of, e.g., at least 5, 10, 25,33, 45, 50, 60, 65, 70, 75, 80, 85, 90, 95, 100, 115, 125, 133, 150,165, 175, or 200 nm and/or up to 1000, 750, 500, 450, 400, 350, 300,275, 250, 225, 200, 175, or 150 nm. Agglomerations of TiO₂ on the fibersmay have an average diameter of, e.g., 100, 150, 200, 250, 300, 350,400, 500, or 750 nm and/or up to 2000, 1750, 1600, 1500, 1400, 1350,1300, 1250, 1200, 1150, 1100, 1050, 1000, 950, 900, 850, 800, or 750 nm.

The TiO₂ agglomerations may be distributed along the length of thefibers, on average, at least every 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75,2, 2.25, 2.5, or 2.75 μm and/or up to 5, 4.5, 4, 3.75, 3.5, 3.25, 3,2.75, 2.5, 2.25, 2, 1.75, or 1.5 μm.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

REFERENCE SIGNS

-   -   1 photovoltaic cells    -   2 traffic signal    -   3 pole    -   4 power source, e.g., battery    -   5 pump    -   6 TiO₂-containing filter    -   7 UV source, e.g., lamp(s)    -   8 cyclone    -   9 polluted (PM_(2.5) containing) air    -   10 treated (“clean”) air

1-19. (canceled)
 20. A cyclonic vehicular traffic pollution controlsystem, comprising: a cyclone having an intake for the vehicular trafficpollution and an output for cycloned air, and a particle filter that isirradiated by a UV source; a power source comprising a solar powercollector mounted on a pole, said solar power collector beingelectrically connected to a battery contained within the pole; and anair treatment system connected to the battery and contained within thetraffic pole, wherein the air treatment system comprises a pump and thecyclone, wherein the particle filter comprises unchargedpolyacrylonitrile fibers having an average diameter of no more than 500nm coated with a layer of anatase TiO₂ nanoparticles applied bycontacting under sonication the polyacrylonitrile fibers with a solutionof an alcohol and the anatase TiO₂ nanoparticles and then drying thepolyacrylonitrile fibers, wherein the anatase TiO₂ nanoparticles haveaverage size of no more than 21 nm and at least 90% of the surface ofthe polyacrylonitrile fibers is covered by the TiO₂ nanoparticles; andwherein the air treatment system is configured to pump the vehiculartraffic pollution through the cyclone and then thorough the particlefilter where it is irradiated by the UV source prior to exhaustingpurified air.
 21. The system of claim 20, wherein the particle filter(6) comprises nanoparticles of titanium dioxide-titanium(IV) oxideanatase.
 22. The system of claim 20, wherein at least 90% of the surfaceof the particle filter (6) is covered by the TiO₂ nanoparticles.
 23. Thesystem of claim 20, wherein the vehicular traffic pollution is airpumped from a traffic intersection.
 24. The system of claim 20, whereinthe pole is a traffic signal.
 25. The system of claim 20, wherein saidair treatment system is entirely contained within the pole.
 26. Thesystem of claim 20, wherein the UV source is sunlight.
 27. The system ofclaim 20, wherein the filter comprises polyacrylonitrile fibers coatedwith a layer of the nanoparticles applied by contacting thepolyacrylonitrile fibers with a solution of an alcohol and the anataseTiO₂ nanoparticles under sonication and then drying thepolyacrylonitrile fibers to produce a filter.
 28. The system of claim20, wherein the filter comprises polyacrylonitrile fibers coated with alayer of the nanoparticles applied by contacting the polyacrylonitrilefibers with a solution of isoamyl alcohol containing 5 to 15 mg/mLanatase TiO₂ nanoparticles under sonication and then drying thepolyacrylonitrile fibers to produce a filter; wherein saidpolyacrylonitrile fibers have an average molecular weight ranging from125 to 175 kDa; and have a polydispersity index ranging from 1.05 to1.15.